1. Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, California 90095–1606 (N.R.A., R.Y., R.B.G.);
2. Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (R.L.F.); and
3. Section of Plant Biology, Division of Biological Sciences, University of California, Davis, California 95616 (J.H.H.)